Can you pour epoxy over oil-based poly?

Yes, you can apply epoxy resin over oiled-based polyurethane.

However, you cannot apply epoxy over water-based polyurethane, as it will not adhere correctly to the surface. Oil-based polyurethane can be used over any surface that has a coating which is unknown or incompatible with epoxy. 

The polyurethane will form a layer between the non-stick surface and the epoxy, allowing it to adhere to the surface without issues.

Note: Oil-based polyurethane is not a replacement for a seal coat of the epoxy.